Reconditioning underground pipelines typically involves removal of existing surface coatings by scraping, sandblasting and/or water blasting, preparation of the pipeline surface by sandblasting and/or water blasting, and the recoating of the surface by painting and/or taping. Reconditioning of underground pipelines is typically done by first digging what is termed a "bellhole" around a small portion of the pipeline. These bellholes typically only expose as little as 18 to 50 feet of pipeline at once in order to reduce stress on the unsupported, exposed pipeline. However, longer segments may be exposed. Once an exposed portion of the pipeline has been reconditioned, it is reburied, or backfilled, and another portion of the pipeline is excavated. This process insures that only a small length of pipeline is unsupported at any one time during the reconditioning operation. Other times reconditioning of underground pipelines is done only at certain places along the length of the pipeline where it is known that repairs are needed.
The nature of these operations is such that reconditioning of an underground pipeline is performed intermittently on short lengths of pipeline. Any machine used to recondition the pipeline in such operations must be repeatedly removed from the excavation to facilitate the continuing backfilling and excavation operations and then installed again in the next excavation.
Present machines for reconditioning pipelines are mostly suited for reconditioning long, continuous runs of pipe. They are either too large or too arduous to install to justify using them intermittently on short lengths of pipeline. Some machines require the use of a side boom or crane to install them on the pipeline; this ties up equipment that can be used elsewhere to backfill or excavate. Other machines require intensive installation operations to secure and adjust the machine around the pipeline for operation. Such machines are inefficient for use in the above type of operations because too much time and expense is used repeatedly removing and installing the machines only for short lengths of pipeline. Other machines are so expensive that their use cannot be justified in situations where a pipeline owner needs only to repair a few places along a pipeline. In such situations manual reconditioning, although slow and of inferior quality, must be used instead.
Reconditioning machines work best when they move at slow continuous speeds along the pipeline. However, during reconditioning operations the existing surface coatings of the pipeline are often uneven and sometimes ripple or bunch up along the pipeline. Also, many pipelines are inclined in the ground. Some of the existing machines do not operate effectively under such conditions because of either a lack of proper traction or lack of any means to compensate for surface irregularities. In some situations, when a ripple or bulge is encountered by the machine, the wheels bind up on the irregularity and the machine is unable to move. In other situations, there is not enough traction between the wheels and the pipeline which causes slipping of the wheel. In either case, the continuous motion of the machine is interrupted and the quality of reconditioning suffers and time is wasted.
There is a need for a machine that can be 1) easily stowed in a van or truck, manually ported into a small excavation, manually installed around a pipeline without the need of a boom or crane, easily adjusted for operation, and then manually ported back out of the excavation and stowed in the van or truck for easy transport to the next excavation and 2) just as easily stowed in its assembled state on a skid that contains the ancillary equipment, such as compressors and blow pots, and then, when ready for use, lowered over a pipeline by a jib crane contained on the same skid. There is also a need for a machine that is inexpensive to manufacture and requires minimal assembly and adjustment steps. There is also a need for such a machine that is capable of any desired reconditioning method whether it be scraping, water blasting, sandblasting, painting, coating or some other method. A need also exists for a reconditioning machine that can operate effectively despite surface irregularities and inclines.